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Chapter 5


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Dax Urbszat

Chapter 5: Variations in Consciousness Notes The Nature Of Consciousness Consciousness is the awareness of internal and external stimuli. • we seem to maintain some degree of awareness even when we are asleep, and sometimes even when we are under anesthesia for surgery. 1. Variations in Awareness and Control. • some of what enters our consciousness seems intentional, other thoughts seem to just meander into our minds. Mind wandering refers to people’s experience of task-unrelated thoughts, thoughts that are not related to what they are intentionally trying to do at a given moment. • mind wandering is less likely to occur if the task you are engaged in is one that requires significant cognitive resources. Controlled processes- judgements or thoughts that we exert some control over, that we intend to occur. Automatic processes- happen without our intentional control or effort. 2. Consciousness and Brain Activity. • consciousness arises from activity in distributed networks of neural pathways. • one of the best physiological indicators of variations in consciousness is the EEG. • different patterns of EEG are associated with different states of consciousness: EEG Pattern Frequency (cps) Typical States of Consciousness Beta (β) 13-24 Normal walking thought, alert problem solving; Alpha (α) 8-12 Deep relaxation, blank mind, meditation; Theta (θ) 4-7 Light sleep Less than 4 Deep sleep Delta (Δ) Biological Rhythms and Sleep Biological rhythms are periodic fluctuations in physiological functioning. • the existence of these rhythms means that organisms have internal “biological clocks” that somehow monitor the passage of time. 1. The Role of Circadian Rhythms. Circadian rhythms are the 24-hour biological cycles found in humans and many other species. • in humans, circadian rhythms are particularly influential in the regulation of sleep. • research indicates that people generally fall asleep as their body temperature begins to drop and awaken as it begins to ascend. each individual may have an “ideal” time for going to bed, which promotes better quality of sleep during • the night. • circadian rhythms generally persist when external time cues are eliminated. • when exposed to light, some receptors in the retina send direct inputs to a small structure in the hypothalamus called the suprachiasmatic nucleus (SCN). the SCN sends signals to the nearby pineal gland,whose secretion of the hormone melatonin plays a key • role in adjusting biological clocks. 2. Ignoring Circadian Rhythms. if you get less than the amount of sleep that you need, you accumulate “sleep debt.” • • getting out of sync with your circadian rhythms causes jet lag. When you fly across several time zones, your biological clock keeps time as usual, even though official clock time changes. • chronic jet lag appears to be associated with measurable deficits in cognitive performance. • people differ in how quickly they can reset their biological clocks to compensate for jet lag. 3. Melatonin and Circadian Rhythms. • melatonin regulates the human biological clock. • it can reduce the effects of jet lag by helping travelers resynchronize their biological clocks. The Sleep and Waking Cycle • sleepers experience quite a bit of physical and mental activity throughout the night. • in addition to an EEG, other 2 crucial devices are an electromyograph(EMG), which records muscular activity and tension, and an electrooculograph(EOG), which records eye movement. Other instruments are also used to monitor heart rate, breathing, pulse rate, and body temperature. 1. Cycling through the Stages of Sleep. during sleep, people cycle through a series of 5 stages. • a) Stages 1-4: • there is no obvious transition point b/w wakefulness and sleep. STAGE 1 it’s a brief transitional stage of light sleep that usually lasts only a few (1-7) min. • • breathing and heart rate slow as muscle tension and body temperature decline. • theta waves are prominent in EEG activity. • hypnic jerks - brief muscular contractions that occur as people fall asleep- occur during this stage. STAGE 2 • it lasts about 10-25 min • during this stage, brief bursts of higher-frequency brain waves, called sleep spindles, appear agains a background of EEG activity. • respiration rate, heart rate, muscle tension, and body temperature continue to decline. STAGES 3 & 4 Slow-wave sleep (SWS) consists of sleep stages 3 and 4, during which high-amplitude, low-frequency delta waves become prominent in EEG recordings. • individuals reach SWS in about an hour and stay there for roughly 30 min. the cycle reverses itself and the sleeper gradually moves back upward through the lighter stages. • b) REM Sleep: REM sleep is a relatively deep stage of sleep marked by rapid eye movements; high-frequency, low- amplitude brain waves; and vivid dreaming. when sleepers reach stage 1 once again, they usually go into the 5th stage of sleep-REM(rapid eye • movement) sleep. • REM sleep was discovered accidentally in the 1950s by grad student William Dement. • this stage tends to be a “deep” stage of sleep-people are relatively hard to awaken from it. • it’s also marked by irregular breathing and pulse rate. muscle tone is extremely relaxed-so much so that body movements are minimal and the sleeper is visually • paralyzed. ✴Although REM is relatively deep stage of sleep, EEG activity is dominated by high-frequency beta waves that resemble those observed when people are alert and awake. • this paradox is probably related to the association b/w REM sleep and dreaming. most dream reports come from the REM stage. • • dreams in REM stage are more frequent, vivid, and memorable than dreams experienced in the other 4 stages. • different stages of sleep may be implicated in memory for different types of tasks or information. c) Repeating the Cycle: • during the course of a night, people usually repeat the sleep cycle about 4 times. • the first REM period is relatively short, lasting only a few minutes. Subsequent REM periods get progressively longer, peaking at around 40-60 min. • NREM intervals tend to get shorter. 2. Age Trends in Sleep. • age alters the sleep cycle • babies only have 2 sleep types: REM and non-REM sleep. • during adulthood, the proportion of REM sleep remains stable, however, the percentage of slow-wave sleep declines dramatically and the percentage of time spent in stage 1 increases slightly, with trends stronger in men than in women. • the average amount of total sleep time also declines with advancing age. 3. Culture and Sleep. • the physiological and psychological experiences of sleep does not appear to vary systematically across cultures. • cultural disparities in sleep are limited to more peripheral matters, such as sleeping arrangements and napping customs. 4. The Neural Bases of Sleep. • sleep depends on the interplay of many neural centres and neurotransmitters. • the rhythm of sleep and waking appears to be regulated by subcortical structures that lie deep within the brain. • reticular formation plays an important part in the regulation of sleep and wakefulness. The ascending reticular activating system (ARAS) consists of the afferent fibres running through the reticular formation that influence physiological arousal. • the ARAS projects diffusely into many ares of the cortex. when these fibres are cut in the brainstem of a cat, the result is continuous sleep. • • many other brain structures are involved as well: - the pons and adjacent areas in the midbrain seem to be critical to the generation of REM sleep. - specific ares in the medulla,thalamus,hypothalamus, and limbic system have also been implicated in the control of sleep and waking. the neurotransmitters serotonin and GABA appear to play especially important roles in the regulation of • sleep, however, other neurotransmitters such as norepinephrine,dopamine, and acetylcholine influence the course of sleep and arousal as well. 5. Doing Without: Sleep Deprivation. a) Sleep Restriction: • partial sleep deprivation, or sleep restriction, occurs when people make do with substantially less sleep than normal over a period of time. • effects depend on the amount of sleep lost and on the nature of the task at hand. • negative effects are most likely when subjects are asked to work on long-lasting, difficult tasks, or when they are asked to restrict their sleep to less than 5 hours from many nights. b) Selective Deprivation: • the effects of REM deprivation has a little impact on daytime functioning and task performance, but it does have some interesting effects on subjects’ pattern of sleeping. as the nights go by in REM-deprivation studies, it becomes necessary to awaken the subjects more and • more often to deprive them of their REM sleep, because they spontaneously shift into REM more and more frequently. • after the experiment is done and the subjects are allowed to sleep without interruption, they experience a “rebound effect”- they spend extra time in REM periods for 1 to 3 nights to make up for their REM deprivation. • REM and slow-wave sleep contribute to the following: - learning that takes place during the day - promoting different types of memory 6. Sleep Disorders. a) Insomnia: Insomnia refers to the chronic problems in getting adequate sleep. • it is the most common sleep disorder. it occurs in 3 basic patterns: • 1) difficulty in falling asleep 2)difficulty in remaining asleep 3)persistent early morning awaking. • insomnia is associated with daytime fatigue, impaired functioning, in elevated risk of accidents, reduced productivity, depression, and increased health problems. Prevalence: • nearly everyone suffers occasional sleep difficulties because of stress, disruption of biological rhythms, or other temporary circumstances. the prevalence of insomnia increases with age and is about 50% more common in women than in men • • some people might suffer from “pseudo-insomnia,” or sleep state misperception, which means that they just think they are getting an inadequate amount of sleep. • about 5% of insomnia patients show sound patterns of sleep. Causes: • it has many causes • it is often a side effect of emotional problems, such as depression, or of significant stress, such as pressures at work. • health problems such as back pain, ulcers, and asthma can lead to insomnia. • the use of certain drugs, such as cocaine, may also lead to insomnia. Treatment: • the most common approach is the prescription of sedative drugs. • benzodiazepine medications, which exert their effects at GABA synapses, are the most widely prescribed sedatives. prescription of sleeping pills have declined significantly in recent decades • • sedatives can be a poor long-term solution for insomnia for a number of reasons: - they have carryover effects that can make people drowsy on the next day - they can also lead to memory decrements - they can cause an overdose in combination with alcohol or opiate drugs. - people can become physically dependent on sedatives - with continuous use, sedatives become less effective - most of them interfere with the normal cycle of sleep • newer sedatives such as zolpidem reduce some of the problems associated with traditional sleeping pills. • melatonin can also be used for treatment. relaxation procedures and behavioural interventions can be helpful for many individuals. • b) Other sleep disorders: Narcolepsy is a disease marked by sudden and irresistible onsets of sleep during normal waking periods. - a person suffering from narcolepsy goes directly from wakefulness into REM sleep, usually for a short period of time (10-20 min). - this is a potentially dangerous condition since some victims fall asleep instantly. - its causes are not well understood, but some people tend to be genetically predisposed to it. - stimulant drugs have been used to treat this disorder Sleep apnea involves frequent, reflexive gasping for air that awakens a person and disrupts sleep. - it occurs when a person stops breathing for a minimum of 10 sec. - heart failure is prevalent among people with some specific types of sleep apnea. - it is usually accompanied by loud snoring - it often leads to insomnia as a side effect Nightmares are anxiety-arousing dreams that lead to awakening, usually from REM sleep. - a person who awakens from nightmares may have difficulty getting back to sleep. - nightmares are most common in children. - persistent nightmares may reflect an emotional disturbance. Night terrors are abrupt awakenings from NREM sleep, accompanied by intense autonomic arousal and feelings of panic. - they happen during stage #4 - they produce remarkable accelerations of heart rate - victims usually let out a p
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